1. Field of the Invention
The present invention relates to a three-dimensional display device which allows stereoscopic viewing and a digital zoom correction method to be carried out in the three-dimensional display device.
2. Description of the Related Art
It has been known to three-dimensionally display a combination of two or more images to provide stereoscopic viewing by using parallax between the images. Such stereoscopic viewing can be achieved by taking two or more images of the same subject with parallax therebetween (which are hereinafter referred to as parallax images) using two or more cameras placed at different positions, and three-dimensionally displaying the parallax images by using parallax between the subject images contained in the parallax images.
Specifically, a stereoscopic image can be generated by combining the two or more images by overlapping the images with providing different colors to the images, such as red and blue, respectively, or by overlapping the images with providing different polarization directions to the images. In these cases, the stereoscopic viewing can be achieved through the use of image separating glasses, such as red-and-blue glasses or polarization glasses, to view the stereoscopic image being displayed and obtain a merged view of the stereoscopic image, which is attained via the automatic focusing function of the eyes (anaglyph system, polarization filter system).
The stereoscopic viewing can also be achieved without using the polarization glasses, etc., by displaying images on a 3D liquid crystal display monitor which allows the stereoscopic viewing, such as of a parallax barrier system or a lenticular system. In this case, a stereoscopic image is generated by alternately arranging vertical strips of the two or more images. Also, the stereoscopic viewing can be achieved by alternately displaying left and right images with changing directions of light beams from the left and right images, which are viewed through the use of the image separation glasses or via an optical element attached on a liquid crystal display monitor (time division system).
With a display device which is capable of digital zoom, an enlarged image can be displayed by enlarging the original image through digital zoom, although the image quality is degraded. With the three-dimensional display device which allows stereoscopic viewing, as described above, when digital zoom is applied to a three-dimensionally displayed image, each of the two-dimensional parallax images is digitally zoomed. Therefore, parallax errors may be introduced among portions of the parallax images being displayed, and this may result in a distorted three-dimensional image or an insufficient or excessive stereoscopic effect during three-dimensional display of the parallax images, and may cause feeling of fatigue and/or discomfort of the user conducting stereoscopic viewing.
In order not to cause the feeling of fatigue and/or discomfort of the user conducting stereoscopic viewing, some methods have been proposed, such as a three-dimensional display method in which a line of sight of the user conducting stereoscopic viewing is detected, and a display surface is always shifted to a position viewed by the user, thereby achieving display of the stereoscopic image which imposes less feeling of fatigue due to inconsistency between convergence and focusing of the eyes (Japanese Unexamined Patent Publication No. 8(1996)-223609), and a method for suppressing distortion of a stereoscopic image by correcting at least one of the parallax images based on determination of a parallax pattern among predetermined parallax patterns (Japanese Unexamined Patent Publication No. 2001-128195).
The methods disclosed in the above-mentioned patent documents, however, do not mention user's feeling of fatigue and/or discomfort when the user conducting stereoscopic viewing is viewing a three-dimensionally displayed image which is digitally zoomed.